The present invention relates to automatic gain control (AGC) circuits, and more particularly to AGC circuits wherein the gain of a signal is adjusted in multiple different frequency bands.
Automatic gain control circuits are widely used in different types of signal processing environments. In the area of commercial broadcasting, automatic gain control circuits are used to compress the dynamic range of an audio frequency signal to render it more compatible for broadcast transmission.
Several known automatic gain control circuits adjust the gain of the input audio signal in multiple different frequency channels. In the multi-band circuit disclosed in the patent to Orban, U.S. Pat. No. 4,249,042, for example, the input audio signal is first separated into three different frequency components, and the gain of each of the three components is adjusted in a separate feedback loop. The three gain adjusted components are then recombined to provide a gain controlled audio output signal. Other multi-band signal processing circuits are disclosed in U.S. Pat. Nos. 4,412,100 and 4,208,548.